A new approach for nitrite determination based on a HRP/catalase biosensor

In this paper, a new concept of enzyme inhibition-based biosensor involving a two enzyme system was developed. The latter displays a signal increase instead of a decrease in the presence of an inhibitor. HRP and catalase were thus separately entrapped into Layered Double Hydroxides (LDH), an anionic clay, as a host matrix. The inner layer was constituted of HRP electrically wired by [Zn₂CrABTS] LDH and the outer layer contained catalase immobilized in [Zn₃AlCl] LDH. Both enzymes catalyzed the decomposition of H₂O₂, HRP its reduction and catalase its breakdown into oxygen and water. Nitrite was selected as a specific inhibitor of catalase. In the presence of H₂O₂, the nitrite addition blocked the H₂O₂ consumption by catalase, inducing thus an increase in the amperometric signal of the H₂O₂ reduction at 0 V by the wired HRP. The optimum configuration of the bi-enzyme biosensor displayed in aerated aqueous solutions, a nitrite sensitivity of 102 μA M^− 1· cm^− 2 with a fast response time, the detective limit being 4 μM.